Microprocessor controlled micro-stepping chart drive

Abstract

A microprocessor controlled micro-stepping chart drive circuit is disclosed. The invention comprises a step clock system, a micro-processor controller and a motor drive circuit. A speed selector establishes a numerical constant within the controller. This numerical constant is decremented down with each pulse of the step clock. When the counter reaches zero, the motor drive circuit is updated. Therefore, the time between updates of the motor drive circuit is a function of the value of the numerical constant.

What is claimed is: 
     
       1. A micro-stepping control circuit for a stepper motor of the type used to drive the chart within an oscillographic recorder, said micro-stepping control circuit comprising: a speed selector means for selecting the speed at which said stepper motor will drive said chart;   a step oscillator means for providing a step frequency pulse signal;   a controller means, said controller means being operatively connected to said speed selector means and said step oscillator means, said controller internally generating a numerical constant whose value is determined by the speed selector means, said numerical constant being either decremented or incremented by at least one pulse from said step oscillator means, said controller means determining if said numerical constant has reached to some predetermined value and then generating a signal indicative thereof; and   drive means operatively connected to said controller means and said stepper motor for driving said stepper motor with a full wave rectified sine and cosine signal broken into staircase increments, said drive means being updated whenever said controller means determines that said numerical constant reaches said predetermined value wherein update for said drive means provides a incremental part of a full step of said stepper motor.   whereby said chart speed is determined by said numerical constant and the time it takes to reach said predetermined value.   
     
     
       2. The micro-stepping control circuit of claim 1 wherein said drive means further comprises a steering circuit to direct which coils of said stepper motor will be powered. 
     
     
       3. The micro-stepping control circuit of claim 1 wherein the drive means drives the four poles of said stepper motor through a linear amplifier with a quadrature sine wave broken into staircase increments. 
     
     
       4. The micro-stepping control unit of claim 1 further comprising a motion detector means having a tachometer and a missing pulse detector for determining when external force has stopped said chart and to re-accelerate said stepper motor if in continuous operation.